1. Field of the Invention
The present invention generally relates to high-pressure die casting processes and, more particularly, toward an improved high pressure die casting process for reducing cycle time in the casting process.
2. Description of Related Art
High pressure die casting is a commonly-used process in which molten aluminum is injected at high pressure into a metal mold by a hydraulically powered piston. The machinery and dies needed for the process are very costly and, accordingly, high pressure die casting is only economical when used for high volume production, such as for making aluminum engine blocks. Such machines are commercially available from a number of manufacturers, including Ube Machinery Inc., of Ann Arbor, Mich.
High pressure die casting machines conventionally include an aluminum injector assembly, a die assembly, a pressure accumulator assembly, a cast-part take-out assembly, and a die spraying assembly. The die assembly includes a fixed die and a movable die, the movable die consisting of a plurality of movable cores. The pressure accumulator supplies pressurized fluid to the entire machine, including the die assembly (for moving of the dies between an open and closed position, and for clamping the dies in the closed position), the injector assembly, die spraying assembly, etc.
To cast an engine block, a plurality of cylinder barrels are manually placed in the dies, and held therein as the dies are closed. Accordingly, the cylinder barrels are insert-molded into the engine block. The dies define side ports through which molten aluminum is injected between the dies by the injector assembly. Following casting of the engine and opening of the dies, the take-out assembly, which is a hydraulically operated device, slides the just-formed engine block out from the die assembly.
After the cast engine block is removed from the die assembly, the die spraying assembly is positioned in the open dies and sprays the dies to clean and cool them in preparation for a subsequent casting operation. The die spraying process includes application of a heat exchange medium (a heated fluid) to maintain portions of the dies at an elevated temperature to facilitate flow and distribution of molten aluminum in the next casting operation. Such a heat exchange medium is expensive, and may cause maintenance problems, as it needs to be reclaimed for recycling, etc.
While the above-referenced conventional die casting apparatus and associated method works satisfactorily, it suffers from the disadvantage that the cycle time is relatively long. The long cycle time is the result of a number of factors inherent in the aforementioned manufacturing process, including the manual insertion of cylinder barrels, delays associated with low volume supplied by the accumulator assembly, and relatively slow operation of the cast-part take out assembly. This long cycle time reduces the number of engines that can be produced in a given time period. Therefore, there exists a need in the art for a method and device that speeds the operation of the high pressure die casting apparatus and thereby reduces the cycle time.